1. Field of the Invention
The present invention relates to a compass provided with a ratchet mechanism. In particular, the present invention also relates to, not only a compass for drawing a circle, but also a compass-cutter for cutting a cloth in circular configuration, the compass-cutter being provided with a ratchet mechanism.
2. Description of the Related Art
FIG. 1 shows an ordinary compass 10, which is used for drawing a circle on, for example, a drawing paper. The compass 10 comprises a pair of legs 11, 15 the open angle therebetween can be adjusted, and a manipulate portion 19 which is provided on a location where the legs 11 and 15 are interconnected. The leg 11 is provided with a needle 12 on its distal end, and the other leg 15 carries a pencil 16 on its distal end.
When a user draws a circle, the user pinches the manipulate portion 19 with fingers, and moves the pencil 16 along a circular path, with the needle 12 stuck on a drawing paper being the center of the circular path. During this operation, it may be difficult to draw a complete 360 degree circle in a single action without re-pinching the manipulate portion with the fingers. Therefore, the user often re-pinches the manipulate portion before completing a circle, and thereafter finishes the circle. This action of re-pinch is cumbersome, and if this re-pinch action is poor, the user can not draw a precise circle, because of unintentional shift of the needle 12, for example.
On the other hand, if the user forcibly tries to draw up a complete circle in a single action, an excessive force may shift the needle 12 relative to the drawing paper, and as a result, a precise circle could not be drawn.
The above disadvantages also are applicable to a compass-cutter for cutting an object in circular configuration.